Information storage devices, which include magnetic storage devices and optical data storage systems, utilize at least one rotatable disk with concentric data tracks containing the information, a transducer for reading data from or writing data to the various tracks, and a head positioning actuator connected to a head for moving it the desired track and maintaining it over the track during read or write operations. The input/output (I/O) transducer is attached to a suspension, and that suspension is attached to an actuator arm of the head positioning actuator. There are typically a plurality of disks separated by spacer rings, the spacer rings allowing heads to access the disks. The disks are stacked on a hub that is rotated by a spindle motor. A housing supports the spindle motor and head actuator and also surrounds the head and disk(s) to provide a substantially environmentally sealed container for the head-disk interface.
Generally a data processing system operates with a host processor including a main memory, typically comprising solid state memory, and a secondary memory comprising one or more storage devices such as a magnetic disk or optical disk storage device. Magnetic disk storage devices typically have a read/write capability, allowing the magnetic disk to be written and read many times. Most optical data storage systems utilize optical media, including disks recorded using rewritable and Write-Once Read-Many (WORM) techniques. Optical disks recorded according to WORM techniques are often used for archival purposes because they can be written only once by a laser. These WORM techniques include irreversible surface ablation and irreversibly combining two or more thin metal films into an alloy of different reflectivity. These optical WORM techniques do not exist for magnetic disk storage devices.
There are some applications in which it is necessary or highly advantageous to provide a permanent, non-alterable version of a file. For example, legal documents, such as Securities and Exchange Commission (SEC) records, stock trading records, business dealings, e-mail, insurance records, etc. should be permanently stored on a media that cannot be altered once the files have been written to the storage device. Similar requirements for permanence exist for medical records and images. Traditionally, WORM functionality has been provided by ablative or alloy optical media used in optical disk drives.
Given the ease with which data can be altered on conventional magnetic storage media, a number of applications use optical disks for providing such “permanent” or “non-alterable” storage. However, there is a need to provide such WORM functionality in a magnetic storage device, such as a hard disk drive (HDD) or a direct access storage device (DASD). One method of providing such functionality is to permit a manual change to the HDD such as setting an external switch or a jumper (pin or wire) to a write-inhibit position to prevent the magnetic storage media from being overwritten. This method suffers from the drawback that the mechanism is easily reversed to make the media writable once again, because the switch or jumper could be temporarily reset to permit alteration of the data, and then reset back to the write-inhibit position. Such a solution is unsatisfactory for the typical WORM applications, which require the integrity of the saved data be maintained. Therefore, a need exists for secure WORM functionality in a magnetic hard disk drive.